Natural gas expansion refrigeration system



Oct. 3, 1961 w. L. MORRISON 3,002,362

' NATURAL GAS EXPANSION REFRIGERATION SYSTEM Filed Sept. 24, 1959 IN V EN TOR. W/uA/w L/flom/som BY men-n CARTER A ffO/Q/VE KS United States Patent 6 3,002,362 NATURAL GAS EXPANSION REFRIGERATION SYSTEM Willard L. Morrison, Lake Forest, 11]., assignor to Liquifreeze Company, Inc, New York, N.Y., a corporation of New York Filed Sept. 24, 1959, Ser. No. 842,129 4 Claims. (Cl. 62-402) This invention relates to improvements in refrigeration systems and has for one object to provide apparatus for and a method of using the high pressure gas in a cross country gas transmission line to provide effective refrigeration at one or more points along the line.

Gas is transmitted in cross country transmission lines at high pressure. At various points along the line where gas is to be used, it passes from the high pressure transmission line through a city gate station or similar discharge and metering plant'for reduction in pressure and discharge for use. 'I propose to take advantage of the reduction in pressure at such point or points to obtain refrigeration.

The normal function of the city gate station is to receive the gas at high pressure (usually about 800 p.s.i.g. and 80 degrees F.) from the cross country transmission system and feed the required gas demand into the city main system, to maintain its pressure at about 25 p.s.i.g. In many instances, it is normal practice to install a gas heater ahead of the break-down regulator to counteract the refrigeration produced by the Joule-Thompson expansion and to assure that no regulator freezing would occur.

The basis of this invention is to utilize the refrigeration effect, which is further intensified by performing the expansion in a polytropic process to a pressure lower than city main pressure and then using the extracted work to compress the expanded gas from this reduced pressure to city main pressure with a turbo machine.

Under ordinary circumstances there will be a continuous flow of gas from the transmission line to the distribution system but as demand varies, the amount discharged will also vary. I propose to take advantage of the continuous supply of part of the gas to continuously recover useful refrigeration.

Such an arrangement will usually only utilize a proportion of the total near to or below minimum city demand and that the city gas regulator would necessarily remain in service to satisfy the daily demand fluctuations.

The flow path through the proposed system will divide the main high pressure gas stream ahead of the city gate station, conducting that quantity representing the city minimum demand requirement to the inlet of the proposed refrigeration plant.

The first step is to thoroughly remove those stream components such as water vapor and carbon dioxide that might deposit on an expander rotor. Next the gas stream is conducted through a precooler to recover any refrigeration ability rejected by the cycle. From the precooler the gas passes through a work extracting turbine where the gas temperature is reduced to 108 degrees F.

The cold exhaust gas will be conducted through a heat exchanger where by heat exchange it will rise in temperature, for example to 55 degrees F. and flow to the inlet gas precooler above referred to, thence to the inlet of the turbo compressor. The turbo compressor will utilize the work produced from the above expansion to compress the gas back to city main pressure, about 25 p.s.i.g.

The heat exchanger may be used in an air refrigeration tunnel to cool ambient air from 80 degrees F. down to 83 degrees R, such cooled air being used to cool any suitable commodity which may pass through the refrigeration tunnel.

ice

On the other hand, the heat exchanger may be used by heat exchange with some element in a liquid nitrogen production plant to furnish part of the cold necessary to obtain liquid nitrogen from the air, such liquid nitrogen may then at atmospheric pressure be shipped to a point where it is used as a refrigerant.

Other objects will appear from time to time throughout the specification and claims.

My invention is illustrated diagrammatically in the accompanying drawing which discloses a flow sheet which illustrates the use of the heat exchanger in an air refrigeration chamber but it will be understood other uses as above referred to for the refrigeration effect may be equally efiective.

Like parts are indicated by like characters throughout the specification and drawings.

In the flow sheet, the cross country transmission line 1 carries gas at high, perhaps 800# pressure. The main 2 leads from the transmission line to a distribution valve 3. From the distribution valve 3, a duct 4 leads to a gas heater 5. From the gas heater 5, a duct 6 leads to the expansion valve 7. A duct 8 leads from the expansion valve 7 to a metering valve 9. The duct 10 leads thence through the control valve 11 to the city main system 12. All the above is in accordance with usual city gate station practice except that the valve 3 may be adjusted to distribute part of the gas from the duct 2 into duct 4 and part of the gas into the duct 13 which leads to the refrigeration part of the system. The duct 13 leads to a carbon dioxide extractor 14 which in turn discharges to a water extractor 15. The gas from the water extractor at 800# pressure and degrees F., passes through the coil 16 in a precooler 17 from which gas is discharged through the duct 18 at 890# pressure and 65 degrees F. to a turbo expander 19 Where it expands, doing work and is reduced in pressure to 25# p.s.i.g. and 108 degrees F. This cold low pressure gas passes through the duct 20 to the refrigeration heat exchange coil 21, thence it passes at 23# pressure and 55 degrees F. through the duct 22 to the heat exchanger 17. From there the gas passes through the duct 23 at 20# pressure and 70 degrees F. to the compressor 24. The compressor is driven by a turbo expander, the work of which passes the gas from 20# up to 25# and discharges it at degrees F. through the duct 25 to the city main control valve 11.

The heat exchanger refrigeration coil 21 may for convenience be located in an air cooling chamber 26. A fan 27 forces ambient air at 80 degrees F. through the heat exchange air refrigeration chamber where it is cooled by the coil 21 and discharged into a product chill tunnel 28 at -83 degrees F. The product to be chilled may enter the tunnel at 29 and be discharged at 30.

As above indicated, the refrigeration heat exchanger 21 may form part of a liquid nitrogen plant, the details of which form no part of the present invention and so are not illustrated but such a plant would utilize the cold gas in the refrigeration heat exchange coil to provide part of the cold necessary for the production of liquid nitrogen, which liquid nitrogen can then 'be used in place or shipped elsewhere as a refrigerant.

The important thing here is that instead of wasting all the heat necessary to protect the city main system from the Joule-Thompson elfect as the pressure drops from, say, 800# down to 25#, I am using part of but not all of the Joule-Thompson effect amplified by the turbo compressor combination to obtain useful refrigeration, whether it is used in place as a coolant or as part of a gas reduction process being beside the point.

I claim:

1. In a gas distribution station having a high pressure gas main, a low pressure gas main and an expansion valve between them, a refrigeration means in parallel with the expansion valve including a heat exchange pre-cooler, a turbo compressor; aturb'o expander and a heat exchange refrigerationcoil, means on the upstream side of theexpansion valve for discharging gas fromthe highpressuremain; conducting it throughthe pre-cooler tothe turbo expander where it does work with resultant fall in temperature and in pressure to apoint below the pressure inthe low pressure main, means for passingthe coldgas through the'refrigeration heat exchange coil and through the pre-cooler, to the turbo compressor where it is compressed to a pressure the same as thatin the low pressure main and means for supplying it to the low pressure main.

2. A gas refrigeration means including in series a source of high pressure warm gas, means for cleaning it, means for cooling it, means for causing it to do work with resultant reduction in pressure and temperature, means for using the resultant cold gas by heat exchange as arefrigerant, means for warming the gas, means for compressing it and means for discharging it from the system.

3. A gas refrigeration system including a heat exchange pre-cooler, a turbo compressor, a turbo expander and a heat exchange refrigeration coil, a source of high pressure warm gas, means for conducting such gas through the heat exchange pre-cooler to the turbo expander where it does work with resultant reduction in temperature and pressure, means for conducting the cold gas from the turbo expander through the heat exchange refrigeration coil and through the heat exchange precooler'to the turbo'cornpressor where his compressed and means for discharging the compressed gas from the system.

4. A gas refrigeration. system including a heat exchange pre-cooler, a-turhocompressor, a turbo expander and a heat exchange refrigeration coil, 21 source of high pressure Warm-gas, means for conductingsuch gas through the heat exchange preacooler' to the turbo expander where it does work with resultant'reduction in pressure and "temperature, means for conducting the cold gas from the turbo'expander through the heat exchange refrigeration coil and through the heat exchange pre-cooler to the turbo compressor where it is compressed to a pressure below that'of' the high pressure gas but above that of the gas inthe refrigeration coil and means for discharging the compressed gas from the system.v

References Cited in the file of this patent UNITED STATES PATENTS 2,002,565 Booth May 28, 1935 2,392,783 Stevens Jan. 8, 1946 2,494,120 Ferro Jan. 10, 1950 2,753,700 Morrison July 10, 1956 2,875,589 Horn Mar. 3, 1959 OTHER REFERENCES Natural Gas and Gasoline Journal, September 1917, page 245. 

